For most space missions, the launch is the headline moment. For BepiColombo, the real milestone arrives years later. After spending nearly eight years weaving through the inner Solar System, the European-Japanese spacecraft is now approaching the point it was designed to reach from the very beginning. As reported by ESA, in November 2026, Mercury is expected to finally capture the spacecraft into orbit, ending one of the longest and most carefully managed planetary journeys ever attempted. The wait has been deliberate rather than unexpected. Travelling to the closest planet to the Sun demands an approach unlike almost any other destination in space, requiring repeated gravity assists and continuous adjustments instead of a direct flight. Once BepiColombo settles into orbit, scientists will begin a new chapter in Mercury exploration, a planet that has remained surprisingly unfamiliar despite sitting in Earth’s cosmic neighbourhood.
Why Mercury remains one of the least explored planets
Mercury has never attracted the steady stream of missions seen at Mars or even Venus. Its position close to the Sun makes every visit technically demanding, leaving astronomers with only a handful of close encounters over the past five decades.The first came through NASA’s Mariner 10 spacecraft during the mid-1970s. Those flybys provided humanity’s earliest detailed views of the scorched world but were never intended to place a spacecraft into orbit. Decades later, NASA’s MESSENGER mission changed that by circling Mercury between 2011 and 2015, transforming understanding of its geology, magnetic field and chemical composition.BepiColombo now becomes only the third mission to arrive at Mercury and just the second designed to orbit the planet, making its arrival a significant addition to a surprisingly short history of exploration.
The unusual path to the Solar System’s innermost planet
Mercury might appear closer than Mars on a map of the Solar System, but distance alone tells very little of the story. Any spacecraft heading inward towards the Sun gathers enormous speed as solar gravity pulls it closer. That extra velocity becomes the main obstacle.Instead of racing directly towards Mercury, BepiColombo has spent years doing almost the opposite. The mission has repeatedly slowed itself down through a carefully planned sequence of planetary encounters. A flyby of Earth, two close passes of Venus and six encounters with Mercury gradually reduced the spacecraft’s speed. At the same time, its ion propulsion system supplied a continuous but gentle push, making small corrections over thousands of hours rather than relying on powerful bursts.The result has been a journey defined by patience instead of speed.
How BepiColombo was designed
Although commonly described as a single spacecraft, BepiColombo actually began its mission as a stack of three connected vehicles.The Mercury Transfer Module has carried the mission through interplanetary space while providing the ion propulsion needed during the long cruise. Attached above it are two independent scientific orbiters that will eventually separate once Mercury has captured the mission.The European-built Mercury Planetary Orbiter will focus on the planet itself, examining its surface, internal structure and geological history. Alongside it, Japan’s Mio spacecraft has a different task. Rather than looking down at Mercury, it will investigate the planet’s magnetic environment, studying the interaction between Mercury, the solar wind and surrounding charged particles.Operating simultaneously gives scientists the opportunity to observe the planet and the space around it at the same time, something previous missions could not achieve.
How engineers kept the mission on track
The original arrival schedule did not survive unchanged.During 2024, engineers identified an unexpected reduction in the performance of the spacecraft’s electric propulsion system. Investigations traced the problem to electrical currents affecting the power distribution system linked with the spacecraft’s solar arrays.Reduced thrust meant the existing flight plan could no longer deliver the spacecraft into Mercury orbit on schedule. Mission specialists redesigned the remaining trajectory, making greater use of Mercury’s own gravity during later flybys to compensate for the weaker propulsion.The revised route preserved the scientific goals of the mission, although it delayed orbit insertion by almost a year. Instead of arriving during late 2025, BepiColombo is now expected to complete the process in November 2026.
How BepiColombo will enter orbit
The mission crossed another important milestone during 2026 when it completed the main phase of ion-powered cruising.Unlike missions that perform one dramatic braking manoeuvre with a large chemical engine, BepiColombo’s arrival unfolds much more gradually. Small propulsion adjustments continue as Mercury’s gravity slowly takes over. The spacecraft will enter a temporary polar orbit before the transfer module is discarded.Only then will the two science orbiters separate and begin moving towards their individual operational paths around the planet. Their full scientific programme is expected to begin during 2027 after commissioning and orbit adjustments have been completed.
Mercury still keeps many unanswered questions
Despite decades of research, Mercury continues to puzzle planetary scientists.Its enormous iron core occupies a much greater proportion of the planet than any other rocky world in the Solar System. The reasons remain uncertain, with several competing theories attempting to explain how such an unusual interior developed.Mercury also possesses a global magnetic field despite its relatively small size. Exactly how that magnetic field has survived for billions of years remains an active area of research.Perhaps the biggest surprise lies near the poles. Although Mercury experiences some of the highest surface temperatures in the Solar System, permanently shadowed craters appear capable of preserving water ice because sunlight never reaches their floors. Understanding the origin and stability of those frozen deposits is one of the objectives awaiting BepiColombo once its scientific observations begin.
